Weekly Pathology Exam - April 21, 2026 (Section A: MCQs)

Question 1

What is the normal pH range of human blood?

Accepted Answer

7.35 - 7.45 — Normal arterial blood pH resides in a narrow range of 7.35 to 7.45 to maintain optimal enzyme function.

Question 2

A patient with COPD has ABG results showing pH 7.28, PaCO2 58 mmHg, and HCO3- 26 mEq/L. What is the primary acid-base disorder?

Accepted Answer

Respiratory Acidosis — The pH is low (<7.35) indicating acidosis, and the PaCO2 is high ( 45 mmHg), which points to a respiratory cause (CO2 retention).

Question 3

Which buffer system is the PRIMARY extracellular buffer system in the body?

Accepted Answer

Bicarbonate buffer system — The Carbonic Acid-Bicarbonate system is the most significant buffer in the extracellular fluid due to the body's ability to regulate CO2 via lungs and HCO3 via kidneys.

Question 4

A diabetic patient presents with rapid, deep breathing (Kussmaul respirations). Which disorder is this compensatory mechanism addressing?

Accepted Answer

Metabolic Acidosis — Kussmaul breathing is a respiratory compensation to blow off CO2 and raise pH in the setting of metabolic acidosis (e.g., Diabetic Ketoacidosis).

Question 5

What is the normal range for arterial PaCO2?

Accepted Answer

35 - 45 mmHg — The reference range for partial pressure of arterial carbon dioxide is 35 to 45 mmHg.

Question 6

A patient with severe vomiting develops metabolic alkalosis. Which mechanism explains this?

Accepted Answer

Loss of H+ and Cl- ions from gastric contents — Vomiting leads to the loss of hydrochloric acid (HCl); the loss of hydrogen and chloride ions results in a relative excess of bicarbonate.

Question 7

What is the normal range for serum bicarbonate (HCO3-)?

Accepted Answer

22 - 28 mEq/L — The standard reference range for serum bicarbonate is typically 22 to 28 mEq/L.

Question 8

Which enzyme in renal tubular cells catalyzes the reaction between CO2 and water to form carbonic acid?

Accepted Answer

Carbonic Anhydrase — Carbonic anhydrase facilitates the rapid interconversion of CO2 and water into carbonic acid, essential for acid-base transport.

Question 9

A patient has ABG results: pH 7.50, PaCO2 30 mmHg, HCO3- 23 mEq/L. What is the diagnosis?

Accepted Answer

Respiratory Alkalosis — The pH is high ( 7.45) indicating alkalosis, and the PaCO2 is low (<35 mmHg), confirming a respiratory etiology.

Question 10

What is the formula for calculating anion gap?

Accepted Answer

Na+ - (Cl- + HCO3-) — The anion gap is calculated by subtracting the sum of measured anions (chloride and bicarbonate) from the measured cation (sodium).

Question 11

Which condition is characterized by an increased anion gap metabolic acidosis?

Accepted Answer

Diabetic Ketoacidosis — DKA results in the accumulation of ketoacids (unmeasured anions), which increases the anion gap.

Question 12

A patient at high altitude develops dizziness and tingling. Which acid-base disorder is most likely?

Accepted Answer

Respiratory Alkalosis — High altitude leads to hypoxia-driven hyperventilation, which blows off excessive CO2, causing respiratory alkalosis.

Question 13

In VHL syndrome, which mechanism explains increased angiogenesis in tumors?

Accepted Answer

Inability to degrade HIF-1α — VHL normally targets HIF-1α for degradation. In VHL syndrome, HIF-1α accumulates and activates VEGF, driving angiogenesis.

Question 14

A tumor reaches 1.8 mm but fails to grow further for years. Why?

Accepted Answer

Lack of nutrients and oxygen without angiogenesis — Without the induction of new blood vessels (angiogenic switch), tumors are limited to a small size (approx 1-2mm) by the diffusion distance of oxygen.

Question 15

During tumor angiogenesis, which combination of activities does MMP-9 perform?

Accepted Answer

Degrades ECM and releases sequestered VEGF — Metalloproteinases (MMPs) degrade the extracellular matrix, facilitating migration and releasing growth factors like VEGF stored in the matrix.

Question 16

Which characteristic would MOST likely be observed in tumor vasculature compared to normal capillaries?

Accepted Answer

Leaky and disorganized structure — Tumor vessels are typically tortuous, dilated, and have leaky walls with irregular basement membranes.

Question 17

Normal p53 prevents angiogenesis by which mechanism?

Accepted Answer

Upregulating anti-angiogenic molecules like thrombospondin-1 — Wild-type p53 stimulates the expression of thrombospondin-1, a potent inhibitor of angiogenesis.

Question 18

Angiostatin, endostatin, and vasculostatin share what common characteristic?

Accepted Answer

They are proteolytic fragments of larger proteins — These are endogenous inhibitors of angiogenesis derived from the cleavage of precursors like plasminogen and collagen.

Question 19

Endothelial cells in tumor vessels contribute to growth through which mechanism BEYOND providing nutrients?

Accepted Answer

Secretion of growth factors like IGF and PDGF — Endothelial cells secrete 'angiocrine' growth factors that support the survival and proliferation of the tumor cells.

Question 20

At which stage of the metastatic cascade do MOST tumor cells fail?

Accepted Answer

Survival in the circulation — Survival in the circulation is very inefficient; most circulating tumor cells (CTCs) are destroyed by immune cells or mechanical stress.

Question 21

Loss of E-cadherin function promotes metastasis through which mechanisms?

Accepted Answer

Decreased cell-cell adhesion and release of β-catenin — E-cadherin holds cells together. Its loss reduces adhesion and releases β-catenin, which can move to the nucleus to promote growth genes.

Question 22

A breast cancer sample shows high expression of CXCR4 and CCR7. Where is it likely to metastasize?

Accepted Answer

Regional lymph nodes and lungs — Chemokines and their receptors play a key role in 'homing' of tumor cells to specific organs like lymph nodes (CCR7) and lungs (CXCR4).

Question 23

During ECM invasion, what is the FIRST step of the four sequential steps?

Accepted Answer

Loosening of cell-cell junctions — The sequence is: 1. Loosening of cell-cell junctions, 2. Degradation of ECM, 3. Attachment, 4. Migration.

Question 24

Cleavage of basement membrane collagen IV and laminin by MMPs serves what purpose beyond degradation?

Accepted Answer

Creates sites for tumor cell attachment and migration — Cleavage exposes cryptic binding sites on ECM components that favor the binding and forward movement of tumor cells.

Question 25

Which lipoprotein transports dietary triglycerides from the intestines to tissues?

Accepted Answer

Chylomicrons — Chylomicrons are formed in the intestinal mucosa to transport exogenous (dietary) lipids.

Question 26

What is the primary function of HDL cholesterol?

Accepted Answer

Reverse cholesterol transport back to the liver — HDL is known as 'good' cholesterol because it removes excess cholesterol from tissues/arteries and returns it to the liver.

Question 27

Which enzyme breaks down triglycerides in adipose tissue during lipolysis?

Accepted Answer

Hormone-Sensitive Lipase — Hormone-sensitive lipase (HSL) mobilizes stored fats into free fatty acids and glycerol.

Question 28

What happens to VLDL as it loses triglycerides in the circulation?

Accepted Answer

It transforms into IDL and then LDL — VLDL remnants (IDL) are further processed to form Low-Density Lipoprotein (LDL).

Question 29

Which hormone promotes lipogenesis and inhibits lipolysis?

Accepted Answer

Insulin — Insulin is an anabolic hormone that promotes fat storage and inhibits the breakdown of adipose tissue.

Question 30

What is the genetic defect in familial hypercholesterolemia (Type IIa)?

Accepted Answer

Mutation in the LDL receptor gene — A defect in LDL receptors leads to decreased clearance of LDL from the blood.

Question 31

Which clinical sign consists of yellowish nodules on the Achilles tendon?

Accepted Answer

Tendinous xanthoma — Tendinous xanthomas are common clinical manifestations of high LDL levels, frequently involving the Achilles tendon.

Question 32

What life-threatening condition can severe hypertriglyceridemia lead to?

Accepted Answer

Acute Pancreatitis — Triglyceride levels above 1000 mg/dL significantly increase the risk of acute pancreatitis.

Question 33

What is lipemia retinalis?

Accepted Answer

Milky appearance of retinal vessels due to high triglycerides — It is a sign of extreme hypertriglyceridemia where the retinal vessels look creamy or white.

Question 34

Which statin is commonly used to lower LDL cholesterol?

Accepted Answer

Atorvastatin — Atorvastatin is an HMG-CoA reductase inhibitor, the primary drug class for LDL reduction.

Question 35

What is the primary metabolic pathway for fatty acid breakdown?

Accepted Answer

Beta-oxidation — Beta-oxidation occurs in the mitochondria to break down fatty acids into Acetyl-CoA.

Question 36

Which apolipoprotein defect is responsible for familial dysbetalipoproteinemia?

Accepted Answer

ApoE — Deficiency or mutation of ApoE results in the accumulation of chylomicron remnants and IDL.

Question 37

The primary difference between Quality Control (QC) and Quality Assurance (QA) is:

Accepted Answer

QC is a component of QA focused on the analytical process — QA is a broader system looking at the whole process, while QC specifically monitors the analytical testing phase.

Question 38

Which type of control chart is most commonly used in Internal Quality Control?

Accepted Answer

Levey-Jennings chart — The Levey-Jennings chart plots daily control values against mean and standard deviation limits.

Question 39

In the pre-analytical phase, which factor is MOST critical?

Accepted Answer

Correct patient identification and sample labeling — Most laboratory errors occur in the pre-analytical phase, with misidentification being a major risk.

Question 40

Positive controls in quality control are used to:

Accepted Answer

Ensure the test can detect the analyte at a known concentration — Positive controls contain the analyte and should give a result within a specific expected range.

Question 41

Which statistical rules are commonly applied to control chart data?

Accepted Answer

The Westgard rules — Westgard rules are a set of multi-rule criteria used to determine if an analytical run is in-control or out-of-control.

Question 42

External Quality Assessment (EQA) primarily serves to:

Accepted Answer

Compare the lab's performance with other laboratories — EQA (Proficiency Testing) involves analyzing unknown samples sent by an external agency to ensure inter-laboratory accuracy.

Question 43

The analytical phase of quality control primarily focuses on:

Accepted Answer

Accuracy and precision of the testing process — The analytical phase encompasses the actual testing of the specimen in the laboratory.

Question 44

Certified Reference Materials (CRMs) are primarily used for:

Accepted Answer

Calibration of instruments — CRMs have highly accurate assigned values used to calibrate instruments or validate methods.

Question 45

Which phase of quality control is responsible for the highest percentage of laboratory errors?

Accepted Answer

Pre-analytical phase — Statistics show approximately 60-70% of lab errors occur before the sample even reaches the analyzer (pre-analytical).

Question 46

In-house controls differ from commercial controls in that they are:

Accepted Answer

Created by the lab using pooled patient samples — In-house controls are prepared by the laboratory itself, often by pooling leftover patient serum.

Question 47

The frequency of running quality control samples typically depends on:

Accepted Answer

Test volume and manufacturer recommendations — QC frequency is determined by the stability of the method and the number of patient samples processed.

Question 48

Multi-level controls are used to:

Accepted Answer

Monitor accuracy across the clinical range (e.g., low, normal, high levels) — Running controls at different levels (e.g., low and high) ensures the assay is accurate across the entire range of possible patient results.

Question 49

Which of the following best describes physiologic hypertrophy?

Accepted Answer

Increased uterine size during pregnancy — Uterine growth in pregnancy is a classic example of physiologic hypertrophy (and hyperplasia) driven by hormonal stimulation.

Question 50

Barrett esophagus is an example of:

Accepted Answer

Metaplasia — Barrett esophagus involves the conversion of squamous epithelium to columnar epithelium in response to acid reflux.

Weekly Pathology Exam - April 21, 2026 (Section A: MCQs)

Questions, Answers & Explanations